Muay Thai is that rare martial
art—it is easy to learn, delivers visible results within two weeks, and is pretty much Chi-free. Translation: Instead of channeling your life force, you kick, punch, and elbow the crap out of a heavy bag (or your opponent). Which is why the centuries-old combat sport is popular among A-listers (Ryan Gosling used the discipline to play a fist-swinging drug smuggler in Only God Forgives) and regular gym-goers.

"Specialty fighting techniques are becoming more mainstream," says Marc Santa Maria, national group-fitness director for Crunch, one of several health clubs that have recently added muay Thai classes. "Guys want authenticity, not 'martial arts–inspired' workouts like Tae Bo."

Guys also want lean frames, sculpted shoulders, solid legs, and a tight midsection, which muay Thai promises. "Everything maximizes the output of energy," says Brandon Levi, owner of New York City's Evolution Muay Thai, who designed this plan. Because it engages your whole body and includes high-intensity intervals during sparring, it's ultra-efficient: "You'll burn at least 500 calories an hour," Levi says. "It creates an incredibly ripped physique."

To get acquainted with muay Thai, sidle up to a heavy bag and knock out two sets of this three-move routine two or three times a week. Finish with 20 reps of The Robot, an ab killer.

1. The Knee (pictured, top right)
Stand at a 45-degree angle to the bag with left foot forward, right foot back, about shoulder-width apart, elbows bent, with right fist at shoulder height and left fist protecting face. Push off left leg as you bend right leg, lifting knee to waist level and driving it forward in one smooth motion to hit the bag. Do 15 reps, then switch sides to complete set.

2. The Strike
Get in starting stance for The Knee (above), but with both fists at chest. Push off right leg as you pivot left foot to the left and hit the bag with right shin, allowing left arm to come up toward chin and swinging right arm out and down as a counterbalance. Do 15 reps, then switch sides to complete set.
3. The Cross
Get in starting stance for The Knee, but reverse foot and fist positioning. Keep right foot planted and rotate left hip and torso as you punch forward with left arm. Do 15 reps, then switch sides to complete set.
+ The Robot
Get into plank position with feet hip-width apart, forearms on floor, and body in a straight line from head to heels. Place left palm on floor and extend left elbow, then right, so that you are in a full push-up position. Then lower back onto left forearm, then right. Repeat, this time starting with right palm. That's 1 rep. Do 20.